Light emitting device

ABSTRACT

A light emitting device includes first and second cladding layers and an active layer therebetween including first and second side surfaces and first and second gain regions, a second side reflectance is higher than a first side reflectance, a first end surface part of the first gain region overlaps a second end surface part of the second gain region in an overlapping plane, the first gain region obliquely extends from the first end surface to a third end surface, the second gain region obliquely extends from the second end surface to a fourth end surface, a first center line connecting the centers of the first and third end surfaces and a second center line connecting the centers of the second and fourth end surfaces intersect, and the overlapping plane is shifted from the intersection point toward the first side surface.

BACKGROUND

1. Technical Field

The present invention relates to a light emitting device.

2. Related Art

In recent years, a high-intensity laser device superior in colorreproducibility has become a promising light emitting device for a lightsource of a display device such as a projector or a monitor display.However, in some cases, there might arise a problem of a speckle noisecaused by mutual interference of scattered light on a screen surface. Tosolve this problem, for example, there has been proposed a method offluctuating the screen to vary the speckle pattern for reducing thespeckle noise in JP-A-11-64789.

However, according to the method disclosed in the document mentionedabove, there might arise another problem that the screen is limited, andthat an additional member for moving the screen such as motor isrequired, and that a noisy sound is caused by the motor or the like.

Further, it is also possible to use a general light emitting diode (LED)for the light source in order to reduce the speckle noise. However,there might be the case in which the LED fails to provide a sufficientoutput power.

SUMMARY

An advantage of the invention is to provide a novel light emittingdevice capable of reducing the speckle noise and providing a high outputpower.

According to an aspect of the invention, there is provided a lightemitting device including a first cladding layer, an active layer formedabove the first cladding layer, and a second cladding layer formed abovethe active layer, wherein the active layer includes a first side surfaceand a second side surface parallel to the first side surface. At least apart of the active layer constitutes a first gain region and a secondgain region, a reflectance of the second side surface is higher thanthat of the first side surface at a wavelength of light generated in thefirst gain region and the second gain region. A part of a first endsurface of the first gain region located on a side of the second sidesurface and a part of a second end surface of the second gain regionlocated on a side of the second side surface overlap with each other inan overlapping plane. The first gain region is disposed from the firstend surface to a third end surface, which is located on the side of thefirst side surface, obliquely to a perpendicular line of the first sidesurface, and the second gain region is disposed from the second endsurface to a fourth end surface, which is located on the side of thefirst side surface, obliquely to the perpendicular line of the firstside surface. A first center line connecting a center of the first endsurface and a center of the third end surface and a second center lineconnecting a center of the second end surface and a center of the fourthend surface have an intersection point, and the overlapping plane isshifted from the intersection point in a direction from the second sidesurface toward the first side surface.

In the light emitting device according to the aspect of the invention,the laser oscillation of the light generated in the gain regions can besuppressed or prevented as described later. Therefore, the mutualinterference of the scattered light can be suppressed, and thus thespeckle noise can be reduced. Further, in the light emitting deviceaccording to the invention, the light generated in the gain regions canproceed while receiving a gain in each gain regions, and then be emittedto outside. Therefore, it is possible to obtain a higher output powerthan that of the general LED of the related art. As described above,according to the aspect of the invention, a novel light emitting devicecapable of reducing the speckle noise with high output power can beprovided.

It should be noted that in the descriptions related to the invention,the term “above” is used in such a phrase as “a specific object(hereinafter referred to as “B”) is formed “above” another specificobject (hereinafter referred to as “A”).” In the descriptions related tothe invention, in such a case as this example, the term “above” is usedin order to include the case of forming B directly on A and the case offorming B on A via something else.

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible that a width of thefirst gain region in the vicinity of the overlapping plane and a widthof the second gain region in the vicinity of the overlapping plane areequal to each other in a plan view, and that the displacement L and thewidth W satisfy the following formula 1, assuming that a displacementbetween the intersection point and the overlapping plane is L, and thewidth of the first gain region in the vicinity of the overlapping regionand the width of the second gain region in the vicinity of theoverlapping region are W.0<L<W  (1)

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible that the displacementL and the width W satisfy the following formula 2.(W/4)≦L≦(3W/4)  (2)

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible that the displacementL and the width W satisfy the following formula 3.L=(W/2)  (3)

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible that the first gainregion is disposed from the first end surface to the third end surfacewith a constant width, and the second gain region is disposed from thesecond end surface to the fourth end surface with a constant width, andthat the width of the first and the second gain regions are equal toeach other.

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible that the second sidesurface is provided with a reflecting section.

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible that a planar shapeof the first gain region and a planar shape of the second gain regionare axisymmetrical with each other about a perpendicular line of theoverlapping plane.

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible that the first gainregion has a reflecting plane between the first end surface and thethird end surface, and the reflecting plane is adapted to reflect lightproceeding in the first gain region. The light emitted from the thirdend surface and the light emitted from the fourth end surface canproceed in the same direction by introducing the reflecting plane in thefirst gain region.

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible in a plan view fromthe side of the first side surface of the active layer that there is nooverlap between the first end surface and the third end surface of thefirst gain region, and that there is no overlap between the second endsurface and the fourth end surface of the second gain region.

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible that a part of thelight generated from the first gain region is reflected by theoverlapping plane and is emitted from the fourth end surface of thesecond gain region, and that a part of the light generated from thesecond gain region is reflected by the overlapping plane and is emittedfrom the third end surface of the first gain region.

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible that a firstelectrode electrically connected to the first cladding layer and asecond electrode electrically connected to the second cladding layer arefurther provided.

It should be noted that in the descriptions related to the invention,the term “electrically connected” is used in such a phrase as “aspecific member (hereinafter referred to as a “member D”) “electricallyconnected” to another specific member (hereinafter referred to as a“member C”).” In the descriptions related to the invention, in such acase as this example, the term “electrically connected” is used in orderto include the case in which the member C and the member D areelectrically connected while having direct contact with each other andthe case in which the member C and the member D are electricallyconnected via another member.

According to another aspect of the invention, in the light emittingdevice of the above invention, it is also possible that a contact layeris further provided above the second cladding layer, and is in ohmiccontact with the second electrode. At least the contact layer and a partof the second cladding layer can constitute a columnar section, and aplanar shape of the columnar section can be identical to that of thefirst gain region and the second gain region.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings, wherein numbers refer to the elements of the device of theinvention.

FIG. 1 is a perspective view schematically showing a light emittingdevice according to the present embodiment.

FIG. 2 is a plan view schematically showing the light emitting deviceaccording to the present embodiment.

FIG. 3 is a cross-sectional view schematically showing the lightemitting device according to the present embodiment.

FIG. 4 is a diagram of an active layer according to the presentembodiment viewed from a first side surface side in a planar manner.

FIG. 5 is a cross-sectional view schematically showing a manufacturingprocess of the light emitting device according to the presentembodiment.

FIG. 6 is a cross-sectional view schematically showing the manufacturingprocess of the light emitting device according to the presentembodiment.

FIG. 7 is a cross-sectional view schematically showing the manufacturingprocess of the light emitting device according to the presentembodiment.

FIG. 8 is a plan view schematically showing the manufacturing process ofthe light emitting device according to the present embodiment.

FIG. 9 is a plan view schematically showing a model used as anexperimental example of the light emitting device according to thepresent embodiment.

FIG. 10 is a graph showing a result of the experimental example of thelight emitting device according to the present embodiment.

FIG. 11 is a plan view schematically showing a light emitting deviceaccording to a modified example of the present embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A preferred embodiment of the invention will be described hereinafterwith reference to the accompanying drawings.

1. Light Emitting Device

Firstly, a light emitting device according to the present embodimentwill be explained with reference to the accompanying drawings. FIG. 1 isa perspective view schematically showing the light emitting device 100according to the present embodiment. FIG. 2 is a plan view schematicallyshowing the light emitting device 100 according to the presentembodiment. FIG. 3 is a cross-sectional view along the III-III lineshown in FIG. 2, and schematically shows the light emitting device 100according to the present embodiment. In FIGS. 1 and 2, a secondelectrode 114 is omitted from illustration for the sake of convenience.Further, the case which the light emitting device 100 is an InGaAlP type(red) semiconductor light emitting device will be explained here.

As shown in FIGS. 1 through 3, the light emitting device 100 includes afirst cladding layer 104, an active layer 106, and a second claddinglayer 108. The light emitting device 100 can further include a substrate102, a contact layer 110, an insulating layer 116, a first electrode112, and a second electrode 114.

As the substrate 102, a GaAs substrate with a first conductivity type(e.g., n-type), for example, can be used.

The first cladding layer 104 is formed on the substrate 102. As thefirst cladding layer 104, for example, an n-type InGaAlP layer can beused. Although not shown in the drawings, it is also possible to form abuffer layer between the first substrate 102 and the first claddinglayer 104. As the buffer layer, an n-type GaAs layer, an n-type InGaPlayer, and so on can be used.

The active layer 106 is formed on the first cladding layer 104. Theactive layer 106 has, for example, a multiple quantum well (MQW)structure obtained by stacking three quantum well structures eachcomposed of an InGaP well layer and an InGaAlP barrier layer.

Some part of the active layer 106 constitutes a plurality of gainregions. In the example shown in the drawing, part of the active layer106 constitutes a first gain region 160 and a second gain region 162.Although not shown in the drawing, it is also possible that the activelayer 106 has another gain region in addition to the first and thesecond gain regions 160, 162, and that the plurality of gain regionsincluding the gain regions 160, 162 is arranged to form an array.

The gain regions 160, 162 can generate light, and the light can receivegains in the gain regions 160, 162. The shape of the active layer 106is, for example, a rectangular solid (including a cube). As shown inFIG. 2, the active layer 106 has a first side surface 105 and a secondside surface 107. The first side surface 105 and the second side surface107 is parallel to each other. At the wavelength of the light generatedin the gain regions 160, 162, the reflectance of the second side surface107 is higher than that of the first side surface 105. For example, asshown in FIGS. 1 and 2, the high reflectance can be obtained by coveringthe second side surface 107 with a reflective section 130. Thereflective section 130 has a high reflective structure such as adielectric mirror or a metallic mirror. More specifically, as thereflective section 130, it is possible to use, for example, a mirrorhaving 10 pairs of layers of SiO₂ and Ta₂O₅ stacked in this order fromthe side of the second side surface 107. It is preferable that thereflectance of the second side surface 107 is 100% or almost 100%. Incontrast, it is preferable that the reflectance of the first sidesurface 105 is 0% or almost 0%. For example, by covering the first sidesurface 105 with an antireflection coating (not shown), it is possibleto obtain low reflectance. It should be noted that the reflectivesection 130 is not limited to the example described above. An Al₂O₃layer, a TiO₂ layer, a TiN layer, an SiN layer, and a multilayer filmthereof, for example, can be used instead.

Each of the gain regions 160, 162 is disposed from the second sidesurface 107 to the first side surface 105 in a direction tilted withrespect to the perpendicular line P of the first side surface 105 in aplan view shown in FIG. 2. Thus, the laser oscillation of the lightgenerated in the gain regions 160, 162 can be suppressed or prevented.The first gain region 160 and the second gain region 162 are disposed inthe directions different from each other. In the example shown in thedrawing, the first gain region 160 is tilted toward one side at an angleθ with respect to the perpendicular line P. The second gain region 162is tilted toward the other side (the side opposite to the one side) atan angle θ with respect to the perpendicular line P.

As shown in FIG. 2, the first gain region 160 has a first end surface170 provided to the second side surface 107 and a third end surface 174provided to the first side surface 105. The second gain region 162 has asecond end surface 172 provided to the second side surface 107 and afourth end surface 176 provided to the first side surface 105. The widthof the first gain region 160 in the first end surface 170 and the widthof the second gain region 162 in the second end surface 172 are equal toeach other. In the example shown in the drawing, the first gain region160 has a constant width W from the first end surface 170 to the thirdend surface 174, and the second gain region 162 has a constant width Wfrom the second end surface 172 to the fourth end surface 176. In otherwords, the planar shape of the first gain region 160 and the second gainregion 162 are parallelogram. In the example shown in the drawing, thewidth W of the first gain region 160 and the width W of the second gainregion 162 are also equal to each other.

A part of the first end surface 170 and a part of the second end surface172 overlap each other in an overlapping plane 178. In other words, itcan be said that the first end surface 170 and the second end surface172 form a single continuous plane. The first end surface 170 canreflect the light generated in the first gain region 160. The second endsurface 172 can reflect the light generated in the second gain region162. The planar shape of the first gain region 160 and the planar shapeof the second gain region 162 can be axisymmetrical with each other withrespect to the perpendicular line P of the first side surface 105. Theplanar shape of the first and the second gain regions 160, 162 can alsobe axisymmetrical with respect to a perpendicular line of theoverlapping plane 178.

Although not shown in the drawings, the first end surface 170 and thesecond end surface 172 can be provided to an opening section formed inthe active layer 106 instead of the side surface of the active layer106.

As shown in FIG. 2, a first center line 160 a connecting the center ofthe first end surface 170 and the center of the third end surface 174 ofthe first gain region 160 and a second center line 162 a connecting thecenter of the second end surface 172 and the center of the fourth endsurface 176 of the second gain region 162 have an intersection point A.The overlapping plane 178 (the second side surface 107) is shiftedtoward the side of the first side surface 105 (+X direction) away fromthe intersection point A. When denoting the displacement between theintersection point A and the overlapping plane 178 (i.e., thedisplacement between the intersection point A and the second sidesurface 107) as L, and the width of the gain regions 160, 162 as W, thedisplacement L and the width W satisfy the formula 1 described below.0<L<W  (1)

Further, the displacement L and the width W preferably satisfy theformula 2 described below.(W/4)≦L≦(3W/4)  (2)

Further, the displacement L and the width W preferably satisfy theformula 3 described below.L=(W/2)  (3)

It should be noted that the first center line 160 a can be the lineintermediate of the two sides of the first gain region 160 that is noton the first end surface 170 or the third end surface 174 in the planview as shown in FIG. 2. Similarly, the second center line 162 a can bethe line intermediate of the two sides of the second gain region 162that is not on the second end surface 172 or the fourth end surface 176.The width W of the first gain region 160 is the distance between the twosides of the first gain region 160 parallel to the first center line 160a in the plan view as shown in FIG. 2. Similarly, the width W of thesecond gain region 162 is the distance between the two sides of thesecond gain region 162 parallel to the second center line 162 a.

If the displacement L and the width W satisfy the relations describedabove, the light emitting device 100 can efficiently emit light. Thedetails explanation of that will be described later.

FIG. 4 is a diagram of the active layer 106 viewed from the side of thefirst side surface 105 in a planar manner. As shown in FIG. 4, the firstend surface 170 and the third end surface 174 of the first gain region160 do not overlap with each other. Similarly, the second end surface172 and the fourth end surface 176 of the second gain region 162 do notoverlap with each other. Thus, it is possible to prevent the directmultiple reflection of the light generated in the first gain region 160between the first end surface 170 and the third end surface 174, and thedirect multiple reflection of the light generated in the second gainregion 162 between the second end surface 172 and the fourth end surface176. As a result, since it is possible to prevent constitution of thedirect resonator, it becomes possible to more reliably suppress orprevent the laser oscillation of the light generated in the gain regions160, 162. Therefore, the light emitting device 100 can emit non-laserlight. In the case shown in FIG. 4, for example, it is sufficient thatthe shift width x between the first end surface 170 and the third endsurface 174 takes a positive value.

As shown in FIGS. 1 and 3, the second cladding layer 108 is formed onthe active layer 106. As the second cladding layer 108, for example, anInGaAlP layer of a second conductivity type (e.g., p-type), can be used.

For example, a pin diode is formed by the p-type second cladding layer108, the active layer 106 with no impurity doped, and the n-type firstcladding layer 104. Each of the first cladding layer 104 and the secondcladding layer 108 has a forbidden band gap larger than that of theactive layer 106 and a refractive index smaller than that of the activelayer 106. The active layer 106 has a function of amplifying the light.The first cladding layer 104 and the second cladding layer 108 have afunction of confining injection carriers (electrons and holes) and thelight in the active layer 106.

In the light emitting device 100, when applying a forward bias voltageof the pin diode between a first electrode 112 and a second electrode114, there occurs recombination of the electron and the hole in the gainregions 160, 162 of the active layer 106. The recombination causes thelight emission. Originating from the generated light, stimulatedemission occurs and the light intensity is amplified inside the gainregions 160, 162. For example, as shown in FIG. 1, a part of the light10 generated in the first gain region 160 is amplified inside the firstgain region 160, and then reflected at the overlapping plane 178 andemitted from the fourth end surface 176 of the second gain region 162 asoutgoing light 20. In this case, the intensity of the part of thegenerated light 10 is also amplified inside the second gain region 162after the reflection. Similarly, a part of the light generated in thesecond gain region 162 is also amplified inside the second gain region162, and then reflected at the overlapping plane 178 and emitted fromthe third end surface 174 of the first gain region 160 as outgoing light22. In this case, the intensity of part of the generated light is alsoamplified inside the first gain region 160 after the reflection. Itshould be noted that some of the light generated in the first gainregion 160 is emitted directly from the third end surface 174 as theoutgoing light 22. Similarly, some of the light generated in the secondgain region 162 is emitted directly from the fourth end surface 176 asthe outgoing light 20. Such light is also amplified inside therespective gain regions 160, 162 in the similar manner.

As shown in FIGS. 1 and 3, the contact layer 110 is formed on the secondcladding layer 108. As the contact layer 110, the layer having an ohmiccontact with the second electrode 114 can be used. As the contact layer110, a p-type GaAs layer, for example, can be used.

The contact layer 110 and part of the second cladding layer 108 can forma columnar section 111. As shown in FIG. 2, the planar shape of thecolumnar section 111 is, for example, the same as that of the gainregion 160, 162. In other words, the current channel between theelectrodes 112, 114 is determined by the planar shape of the columnarsection 111, for example, and as a result, the planar shapes of the gainregions 160, 162 are determined. Although not shown in the drawings, thecolumnar section 111 can also be constituted with, for example, thecontact layer 110, a part of the second cladding layer 108, a part ofthe active layer 106, and a part of the first cladding layer 104.Although not shown in the drawings, the side surfaces of the columnarsection 111 can be tilted.

As shown in FIGS. 1 and 3, the insulating sections (also referred to asthe insulating layer) 116 can be disposed on the second cladding layer108 and lateral to the columnar sections 111. The insulating sections116 have contact with the side surfaces of the columnar sections 111.The upper surfaces of the insulating sections 116 can be contiguous tothe upper surface of the contact layer 110. As the insulating section116, for example, an SiN layer, an SiO₂ layer, and a polyimide layer canbe used. If such materials are used as the insulating sections 116, thecurrent between the electrodes 112, 114 can flow through the columnarsections 111 while avoiding the insulating sections 116. It is possiblefor the insulating sections 116 to have a refractive index smaller thanthe refractive index of the active layer 106. In this case, theeffective refractive index of the vertical section in which theinsulating section 116 is provided becomes smaller than that of thevertical section in which the insulating section 116 is not provided,namely the section in which the columnar section 111 is provided. Thus,it becomes possible to efficiently confine the light inside the gainregions 160, 162 with respect to the planar direction. It is alsopossible to eliminate the insulating sections 116. In other words, theinsulating sections 116 can be an air. In this case, it is required toexclude the active layer 106 and the first cladding layer 104 from thecolumnar sections 111, or to prevent the second electrode 114 fromhaving direct contact with the active layer 106 and the first claddinglayer 104.

The first electrode 112 is formed on the entire bottom surface of thesubstrate 102. The first electrode 112 can have contact with the layer(the substrate 102 in the example shown in the drawings) having an ohmiccontact with the first electrode 112. The first electrode 112 iselectrically connected to the first cladding layer 104 via the substrate102. The first electrode 112 is one side of the electrodes for drivingthe light emitting device 100. As the first electrode 112, for example,a stacking layer obtained by forming a Cr layer, an AuGe layer, an Nilayer, and an Au layer in this order from the side of the substrate 102can be used. It is also possible to form the electrode 112 by disposinga second contact layer (not shown) between the first cladding layer 104and the substrate 102, exposing the second contact layer using a dryetching process, and then disposing the first electrode 112 on thesecond contact layer. Thus, a single-sided electrode structure can beobtained. This form is particularly effective in the case that thesubstrate 102 is an insulating layer.

As shown in FIG. 3, the second electrode 114 is formed on the contactlayer 110 (on the columnar sections 111). Although not shown in thedrawings, the second electrode 114 can be formed on the entire uppersurfaces of the contact layer 110 and the insulating sections 116. Thesecond electrode 114 is electrically connected to the second claddinglayer 108 via the contact layer 110. The second electrode 114 is theother side of the electrodes for driving the light emitting device 100.As the second electrode 114, for example, a stacking layer obtained byforming a Cr layer, an AuZn layer, and an Au layer in this order fromthe side of the contact layer 110 can be used. As shown in FIG. 2, thecontact surface between the second electrode 114 and the contact layer110 has substantially the same planar shape as those of the gain regions160, 162.

As an example of the light emitting device 100, the case of InGaAlP typeis explained above. However, according to the present embodiment, anymaterial type capable of forming a light emitting gain region can beused in the light emitting device 100. In the case of semiconductormaterials, such as an AlGaN type, an InGaN type, a GaAs type, an InGaAstype, a GaInNAs type, a ZnCdSe type can be used.

The light emitting device 100 according to the present embodiment can beapplied to the light source for a projector, a monitor display, anillumination device, and a measuring device, for example.

The light emitting device 100 according to the present embodiment hasthe following features, for example.

According to the light emitting device 100, the laser oscillation of thelight generated in the gain regions 160, 162 can be suppressed orprevented as described above. Therefore, the speckle noise can bereduced. Further, according to the light emitting device 100, the lightgenerated in the gain regions 160, 162 can proceed in the gain regions160, 162 while receiving a gain to be emitted to outside. Therefore, itis possible to obtain a higher output power than that of the generallight emitting diode (LED) of the related art.

According to the light emitting device 100, the displacement L betweenthe intersection point A and the overlapping plane 178 and the width Wof the gain regions 160, 162 can satisfy the formula 1 described above,further the formula 2 described above, and still further the formula 3described above. Therefore, the light emitting device 100 can emit thegenerated light efficiently. The details thereof will be describedlater.

According to the light emitting device 100, the part of the light 10generated in the first gain region 160 is reflected by the overlappingplane 178, and can also proceed in the second gain region 162 whilereceiving a gain. Further, the same can be applied to part of the lightgenerated in the second gain region 162. Therefore, according to thelight emitting device 100, since the distance for amplifying theintensity of the light becomes longer compared to the case that thelight is not reflected by the overlapping plane 178, the higher outputpower can be obtained.

2. Method of Manufacturing Light Emitting Device

Then, a method of manufacturing the light emitting device according tothe present embodiment will be explained with reference to theaccompanying drawings. FIGS. 5 through 7 are cross-sectional viewsschematically showing the manufacturing process of the light emittingdevice 100 according to the present embodiment corresponding to FIG. 3.FIG. 8 is a plan view schematically showing the manufacturing process ofthe light emitting device 100 according to the present embodiment. InFIG. 8, a second electrode 114 is omitted from illustration for the sakeof convenience.

As shown in FIG. 5, the first cladding layer 104, the active layer 106,the second cladding layer 108, and the contact layer 110 are epitaxiallygrown on the substrate 102 in this order. As a method for growing thelayers epitaxially, a metal organic chemical vapor deposition (MOCVD)method, a molecular beam epitaxy (MBE) method, and so on can be used.

As shown in FIG. 6, the contact layer 110 and the second cladding layer108 are patterned. The patterning is performed by using, for example, aphotolithography technique or an etching technique. According to thepresent process, the columnar sections 111 can be formed.

As shown in FIG. 7, the insulating sections 116 are formed so as tocover the side surfaces of the columnar sections 111. Firstly, aninsulating layer (not shown) is formed as a film above the secondcladding layer 108 (including the surface of the contact layer 110)using, for example, a chemical vapor deposition (CVD) method or acoating method. Subsequently, the upper surface of the contact layer 110is exposed using, for example, an etching technique. Accordingly, theinsulating sections 116 can be formed.

Subsequently, the second electrode 114 is formed on the contact layer110. The second electrode 114 is formed using, for example, a vacuumdeposition method.

Subsequently, the first electrode 112 is formed under the bottom surfaceof the substrate 102. The manufacturing method of the first electrode112 is, for example, the same as that of the second electrode 114described above. The order of forming the first electrode 112 and thesecond electrode 114 is not particularly limited. According to theprocess described above, a plurality of light emitting patterns can beformed inside a wafer.

Subsequently, as shown in FIG. 8, scribing lines 3 (3 a, 3 b, 3 c) forseparating a plurality of light emitting patterns 101 (101 a, 101 b, 101c) are provided to a wafer 1 having the plurality of light emittingpatterns 101. Although the number of light emitting patterns 101 isthree in the example shown in the drawing, the number is notparticularly limited. The scribing lines 3 are formed using, forexample, a diamond cutter or a laser. The light emitting device 100 canbe obtained by cleaving the wafer 1 along the scribing lines 3 toseparate the light emitting patterns 101. The scribing lines 3 can beprovided for forming a cleavage surface including the second sidesurface 107. The scribing lines 3 are preferably formed at a positionwith a displacement L from the intersection point A of the first centerline 160 a and the second center line 162 a toward the +X direction(toward the side of the first side surface 105). The displacement Lpreferably has a value that is half as large as the width W of the gainregions 160, 162. In other words, the displacement L between thescribing lines 3 and the intersection point A preferably satisfies theformula 3 described above. In this invention, in case of forming thescribing lines 3 a on both sides of the light emitting pattern 101 a asshown in the drawing, the displacement L between the intersection pointA and the scribing line 3 denotes the displacement between theintersection point A and the straight line connecting both sides of thescribing lines 3 a.

More specifically, as shown in FIG. 8, the scribing lines 3 a areprovided to the light emitting pattern 101 a so as to satisfy theformula 3 described above, the scribing lines 3 b are provided to thelight emitting pattern 101 b so as to satisfy the formula 3 describedabove, and the scribing lines 3 c are provided to the light emittingpattern 101 c so as to satisfy the formula 3 described above. In otherwords, the scribing lines 3 can be formed so as to satisfy the formula 3described above with respect to the respective light emitting patterns101. Therefore, it is possible that each of the scribing lines 3 is notcontinuous like a straight line, and is formed as a broken line as shownin FIG. 8, for example. Thus, it becomes possible to form the cleavagesurfaces more accurately so as to satisfy the formula 3 with respect tothe respective light emitting patterns 101. In particular, it iseffective when displacement occurs in the patterning process and each ofthe light emitting patterns 101 is not formed along with the crystalplane.

Further, misalignment in manufacturing process might occur in thescribing process (forming scribing lines 3) themselves. For example,even if the scribing lines are formed aiming at the intersection pointA, the scribing lines might be shifted in the −X direction (the oppositeside of the first side surface 105) from the intersection point A. Inthis case, as described later, the light emitting device fails to emitlight efficiently. Therefore, it is preferable to manufacture thescribing lines 3 aiming at the position satisfying the formula 3described above in order to enhance the tolerance for the misalignmentin the manufacturing process, and to obtain in a good yield the lightemitting device 100 capable of emitting light efficiently.

As shown in FIGS. 1 and 2, the reflective section 130 is formed on theentire surface of the side of the second side surface 107. Thereflective section 130 is formed using, for example, a CVD method, asputtering method, or an ion assisted deposition method.

According to the process described above, the light emitting device 100can be manufactured.

According to a method for manufacturing the light emitting device 100,the light emitting device 100 capable of efficiently emitting the lightcan be obtained. The details thereof will be described later.

3. Experimental Example of Light Emitting Device

Then, an experimental example of the light emitting device according tothe present embodiment will be explained with reference to theaccompanying drawings. Specifically, a simulation in a model M obtainedby modeling the first gain region 160, the second gain region 162, andthe reflective section 130 of the light emitting device 100 according tothe present embodiment will be explained. FIG. 9 is a plan viewschematically showing the model M of the light emitting device 100according to the present embodiment. FIG. 10 is a graph showing a resultof the simulation in the model M of the light emitting device 100according to the present embodiment.

Firstly, the configuration of the model M will be explained.

In the model M, the vicinity of the overlapping plane 178 of the lightemitting device 100 according to the present embodiment is analyzed.More specifically, as shown in FIG. 9, an end of the calculation area onthe side of the third end surface 174 and on the side of the fourth endsurface 176 is defined as a calculation end section B-B line. The light12 with the intensity I₁₂ proceeding from the vicinity of thecalculation end section B-B line of the first gain region 160 toward thefirst end surface 170 are generated, and the light 13 with the intensityI₁₃ proceeding from the first end surface 170 toward the calculation endsection B-B line and the light 14 with the intensity I₁₄ having reachedthe calculation end section B-B line of the second gain region 162 ismonitored. It should be noted that in the model M, there used aabsorbing boundary conditions that almost all light having reached thecalculation end section B-B line is transmitted through the B-B linewithout reflected toward outside. In other words, all of the light 14having reached the calculation end section B-B line is transmittedthrough the B-B line and then emitted to outside of the calculation area(to the +X direction side from the calculation end B-B line), and thereis no light returning to inside the gain regions 160, 162. Therefore,even if the end surface of the first gain region 160 in the calculationarea overlaps when viewed from the side of the first side surface 105 ina planar manner by limiting the calculation area, the multiplereflection is never caused inside the first gain region 160. Similarly,also in the second gain region 162, the multiple reflection is nevercaused. As described above, since the multiple reflection is nevercaused in the model M, there is no chance to form a resonator.

In the model M, the intensity I₁₄ of the light 14 is monitored whilefixing the position of the first side surface 105, and varying thedisplacement L between the second side surface 107 (the overlappingplane 178) and the intersection point A of the first center line 160 aand the second center line 162 a. In the model M, it is assumed that thelight 12 proceeds inside the first gain region 160 from the vicinity ofthe calculation end section B-B line of the first gain region 160 towardthe first end surface 170, then proceeds inside the second gain region162 via the overlapping plane 178, then reaches the calculation endsection B-B line of the second gain region 162 as the light 14, and isthen transmitted to outside the calculation area. In the model M, it isassumed that the light 12 does not receive a gain in the gain regions160, 162 for the sake of calculation convenience. Therefore, in themodel M, by monitoring the intensity I₁₄ of the light 14, it becomespossible to calculate the loss with respect to the intensity I₁₂ of thelight 12.

In the model M, it is assumed that the effective refractive index of thegain regions 160, 162 (i.e., the effective refractive index of thecolumnar section) is 3.346, and that of the region without constitutingthe gain regions 160, 162 (i.e., the effective refractive index of theoutside of the columnar section) is 3.344. In the model M, it is assumedthat the angles θ of the gain regions 160, 162 with respect to theperpendicular line P of the first side surface 105 are both 10 degrees.In the model M, as the reflective section 130, for example, a dielectricmirror having 10 pairs of layers of SiO₂ and Ta₂O₅ stacked in this orderfrom the side of the second side surface 107. The SiO₂ layer is arrangedto have a refractive index of 1.43, and the thickness of one layer ofwhich is 113.61 nm. The Ta₂O₂ layer is arranged to have a refractiveindex of 2.16, and the thickness of one layer of which is 75.22 nm. Inthe model M, the simulation is performed by setting the width W of thegain region 160, 162 to be 5 μm and 10 μm.

Then, the result of the simulation will be explained.

In the graph shown in FIG. 10, the horizontal axis represents thedisplacement L, and the vertical axis represents an intensity ratio R.In the displacement L on the horizontal axis, the point at which theintersection point A and the second side surface 107 overlap with eachother corresponds to zero, the case in which the second side surface 107is displaced to the side of the first side surface 105 (+X direction)corresponds to the positive value (i.e., the value of the displacement Lis positive), and the case in which the second side surface 107 isdisplaced to opposite the side of the first side surface 105 (−Xdirection) corresponds to the negative value (i.e., the value of thedisplacement L is negative). The intensity ratio R on the vertical axisrepresents the ratio (I₁₄/I₁₂×100(%)) of the intensity I₁₄ of the light14 with respect to the intensity I₁₂ of the light 12. In other words, itcan be said that the higher the intensity ratio R is, the smaller theloss of the light is, and the more efficiently the light can be emitted.

According to FIG. 10, it is understood that the intensity ratio R in therange (the range of the formula 1 described above) satisfying 0<L<W issubstantially equivalent to or higher than the intensity ratio R at L=0.Further, it is understood that the intensity ratio R in the rangesatisfying (W/4)≦L≦(3W/4) (the range of the formula 2 described above)is surely higher than the intensity ratio R at L=0. Further, it isunderstood that in the case of L=(W/2) (the case of the formula 3) theintensity ratio R takes the maximum value, and the loss of light becomesminimum.

The reason that the loss of light becomes smaller due to therelationship between the displacement L and the width W described abovecan be inferred as follows.

The distance between the first gain region 160 and the second gainregion 162 decreases as the first and second gain regions 160, 162 comecloser to the second side surface 107. Then, due to the evanescentcoupling, some component of the light proceeding in the first gainregion 160 toward the first end surface 170 begins to move to the secondgain region 162 without going via the overlapping plane 178. In otherwords, the light proceeding in the first gain region 160 toward thefirst end surface 170 senses the second gain region 162 as a highlyrefractive region, and some of the light begins to move toward thesecond gain region 162 and thereby be deflected. Assuming the case thatthe refractive index difference between the gain regions 160, 162 andthe surrounding region is small, part of the light being deflectedtoward the second gain region 162 might pass through the second gainregion 162 directly to cause the loss. In order to prevent such lightfrom being loss and to input such light in the second gain region 162,it is required to make the reflecting plane come closer in accordancewith the path of the light thus deflected. Therefore, it can be inferredthat the intensity ratio R can be raised because such light loss can bereduced by setting the L to be a positive value and the relationshipbetween the displacement L and the width W to be the relationshipexpressed by the formula 1, preferably the formula 2, and furtherpreferably the formula 3 described above.

As described above, in the light emitting device 100, the displacement Land the width W can satisfy the formula 1, further the formula 2, andstill further the formula 3 described above. Therefore, in the lightemitting device 100, the loss of light can be reduced, and the light canbe emitted efficiently. Further, since the light emitting device 100 canemit light efficiently, miniaturization thereof can be achievedaccordingly.

4. Modified Example

Then, a light emitting device 200 according to a modified example of thepresent embodiment will be explained with reference to the accompanyingdrawings. FIG. 11 is a perspective view schematically showing the lightemitting device 200. Hereinafter, in the light emitting device 200according to the modified example of the present embodiment, theconstituents thereof having the same functions as those of theconstituents of the light emitting device 100 according to the presentembodiment will be denoted by the same reference symbols, and detailedexplanations thereof will be omitted. In FIG. 11, the second electrode114 is omitted from illustration for the sake of convenience.

As shown in FIG. 11, in the light emitting device 200, the first gainregion 160 is provided with a reflecting plane 261 between the first endsurface 170 and the third end surface 174. In the example shown in thedrawing, the reflecting plane 261 is disposed on a third side surface205 perpendicular to the first side surface 105 and the second sidesurface 107 of the active layer 106. In the first gain region 160, thelight 210 proceeding from the first end surface 170 to the reflectingplane 261 can be reflected (e.g., totally reflected) by the reflectingplane 261 and thereby proceed from the reflecting plane 261 toward thethird end surface 174. Subsequently, the light 210 can be emitted fromthe third end surface 174 as the outgoing light 22. In the example shownin the drawing, the light 22 emitted from the third end surface 174 andthe light 20 emitted from the fourth end surface can proceed in the samedirection.

Although not shown in the drawing, the reflecting plane 261 can beprovided only to the second gain region 162 instead of the first gainregion 160, or can be provided to each of the gain regions 160, 162.Further, the third end surface 205 provided with the reflecting plane261 can also be provided with a reflecting section. The reflecting plane261 can also be provided to an opening section formed in the activelayer 106 by etching instead of the third end surface 205. The light 22emitted from the third end surface 174 and the light 20 emitted from thefourth end surface can also proceed in a converging direction.

According to the light emitting device 200, the light 22 emitted fromthe third end surface 174 and the light 20 emitted from the fourth endsurface 176 can proceed in the same direction or a converging direction.Thus, although not shown in the drawings, it becomes possible tominiaturize the optical system (the optical system to which the outgoinglight 20, 22 incidents) compared to the case that the two outgoing lightproceed in a diverging direction.

As described above, although the embodiment of the invention isexplained in detail, it should be easily understood by those skilled inthe art that various modifications not substantially departing from thenovel matters and the effects of the invention are possible. Therefore,such modified examples should be included in the scope of the invention.

The entire disclosure of Japanese Patent Application No: 2009-062502,filed Mar. 16, 2009 is expressly incorporated by reference herein.

1. A light emitting device comprising: a first cladding layer; an activelayer formed above the first cladding layer; and a second cladding layerformed above the active layer, wherein the active layer includes a firstside surface and a second side surface parallel to the first sidesurface, at least a part of the active layer configures a first gainregion and a second gain region, the first gain region has a first endsurface on the second side surface and a third end surface on the firstside surface, and the second gain region has a second end surface on thesecond side surface and a fourth end surface on the first side surface,a second reflectance of the second side surface is higher than a firstreflectance of the first side surface at a wavelength range of lightgenerated in the first gain region and the second gain region, a part ofthe first end surface of the first gain region overlaps with the secondend surface of the second gain region to configure an overlapping plane,a first center line connecting a first center of the first end surfaceand a third center of the third end surface is angled relative to aperpendicular direction relative to the first side surface, a secondcenter line connecting a second center of the second end surface and afourth center of the fourth end surface is angled relative to theperpendicular direction, and the first center line and the second centerline intersect at an intersection point, the overlapping plane isshifted from the intersection point in a shift direction from the secondside surface toward the first side surface in a plan view, a width W ofthe first gain region in the vicinity of the overlapping plane and thewidth W of the second gain region in the vicinity of the overlappingplane are equal to each other, and when a length between theintersection point and the overlapping plane is L, the width W and thelength L satisfy the following formula 1;0<L<W  (1).
 2. The light emitting device according to claim 1, whereinthe displacement L and the width W satisfy the following formula 2(W/4)≦L≦(3W/4)  (2).
 3. The light emitting device according to claim 2,wherein the displacement L and the width W satisfy the following formula3L=(W/2)  (3).
 4. The light emitting device according to claim 1, whereinthe first gain region is disposed from the first end surface to thethird end surface with a first constant width W1, the second gain regionis disposed from the second end surface to the fourth end surface with asecond constant width W2, and the first and second constant widths W1,W2 are equal to each other.
 5. The light emitting device according toclaim 1, wherein the second side surface is provided with a reflectingsection.
 6. The light emitting device according to claim 1, wherein aplanar shape of the first gain region and a planar shape of the secondgain region are axisymmetrical with each other with respect to aperpendicular line that is parallel to the perpendicular direction andthat extends from the overlapping plane.
 7. The light emitting deviceaccording to claim 1, wherein the first gain region has a reflectingplane which reflects light proceeding in the first gain region betweenthe first end surface and the third end surface, and light emitted fromthe third end surface and light emitted from the fourth end surfaceproceed in the same direction or converging direction.
 8. The lightemitting device according to claim 1, wherein in a plan view viewed fromthe side of the first side surface of the active layer, there is nooverlap between the first end surface and the third end surface of thefirst gain region, and there is no overlap between the second endsurface and the fourth end surface of the second gain region.
 9. Thelight emitting device according to claim 1, wherein part of the lightgenerated from the first gain region is reflected by the overlappingplane, and is emitted from the fourth end surface of the second gainregion, and part of the light generated from the second gain region isreflected by the overlapping plane, and is emitted from the third endsurface of the first gain region.
 10. The light emitting deviceaccording to claim 1, further comprising: a first electrode electricallyconnected to the first cladding layer; and a second electrodeelectrically connected to the second cladding layer.
 11. The lightemitting device according to claim 10, further comprising: a contactlayer formed above the second cladding layer, and having an ohmiccontact with the second electrode, wherein at least the contact layerand a part of the second cladding layer constitute a columnar section,and the columnar section has a planar shape identical to a planar shapeof the first gain region and the second gain region.